1. Field of the Invention
The present invention relates to a method and apparatus for clipping figures using predetermined frames.
2. Description of the Related Art
According to a conventional method, in order to execute processing for painting out an area (a portion indicated by hatched lines in FIG. 1A) surrounded by boundary lines using a graphic display, all boundaries are written in a frame memory, and then a necessary portion is painted out while positions of the boundaries are read out along scanning lines. In this case, however, the boundaries must be closed, thereby imposing limitations.
In graphic processing, it is generally practiced that a portion of a figure is cut out and displayed using predetermined clipping frame W (refer to FIG. 1A). For example, in a figure shown in FIG. 1A, when a figure (refer to FIG. 1B) cut out by clipping frame W is to be displayed with the above method, new boundary lines B which do not exist before the figure is cut out must be extracted. Since extraction of boundary lines B is performed by a processor, a processing speed is decreased.
Therefore, it is desirable that extraction of new boundary lines which do not exist in a figure to be clipped is performed at a high speed.